The Social Security Administration (SSA) recently updated their on-line materials to reflect that SNTs and Able accounts are exempt from being a countable resource. The primary exempt resources are the home a Medicaid/SSI recipient lives in and the land as well as one vehicle (regardless of value) that is used for transportation. Also, household goods and personal effects are exempt.
This all becomes important when trying to qualify for SSI and/or Medicaid benefits after suffering a personal injury. Complex planning has to be done to make sure that one doesn't lose eligibility permanently for needs based government assistance programs. SSI and most Medicaid programs tied to SSI have a 2k asset cap for those that are single and 3k if married. So exempt assets are important as they don't count towards the cap.
To learn more about SSI resources and the program itself, SSA has a helpful webpage: https://www.ssa.gov/ssi/text-understanding-ssi.htm